Shear-Thinning Properties of Blood in Large Arteries

Newtonian and non-Newtonian viscous models have been widely applied in many biofluid research areas in order to understand the relationship between hemodynamics and vascular disease. Using Newtonian blood in modeling blood flow for large arteries in cardiovascular hemodynamics has become a common assumption in much of the literature. However, the criteria of size and flow regime that are suitable for such an assumption have not been very well defined. This study reviews the difference between two of the most commonly used viscous blood-flow models found in the literature: the Newtonian model with a constant dynamic blood viscosity of  = 0.0035 Pa∙s, and the Carreau-Yasuda nonNewtonian model, which accounts for the shear-thinning properties of blood. CFD simulations were conducted under steady-state and transient-state conditions in a straight tube flow. For the steady-state condition, tube diameters in the range of 2 to 16 cm were tested with Reynolds numbers in the range of 520 < Re < 1560. For the transient-state condition, flow was characterized with a mean Reynolds number Remean = 520 and a Womersley number in the range of 10.00 < < 27.59. Results suggest that the difference between the shear-thinning non-Newtonian model and the Newtonian model is increased under flow conditions where reversed flow is expected. However, such a difference is reduced when the  increases.